On a certain level merely promoting biomass is sufficient since human civilization doesn't need maximum biodiversity or anything like that.
On the other hand, for those who believe in stewardship then there are many layers to consider, including preservation of biodiversity. When speaking of roles, having two plants in the same location isn't enough to indicate that they serve the same roles. On the contrary, invasives tend to be quite good at destroying existing roles which otherwise would've been held in a cooperative balance.
Since it's not that difficult as thinking adults to make small choices that lead to big changes in this regard, there's no real problem with promoting natives. For instance, there's millions of acres of lawn in the US which could host things other than turf grass and non-native ornamentals.